Pharmacological evaluation of Ocimum basilicum leaf extract for targeting third instars larvae of anopheles mosquitoes: a promising natural approach to malaria vector control.

Abstract

Malaria continues to represent one of the major pressing of public health challenges wordwide, particularly in tropical and subtropical countries where environmental conditions favour vector development and disease transmission. This disease is caused by Plasmodium parasite, which is transmitted to humans, following the bites of infected female Anopheles mosquitoes. Therefore, effective vector control requires critical component of comprehensive malaria prevention and control strategies. This study investigated the larvicidal efficacy of Ocimum basilicum leaf extract on third instars larvae of Anopheles mosquito. Fresh Ocimum basilicum leaf extract was washed, shade- dried and milled to fine powder. Maceration method was used to obtain the leaf extract for the larval toxicity test. Larvae were reared according to Pavela method. Qualitative and quantitative analyses of extract were carried out using standard analytical methods. Five concentrations - 250, 500, 750, 1000 and 1250 ppm of the extracts were tested. Four replicates were maintained for each concentration and mortality tests of the larvae, recorded at 24, 48 and 72 hours. The results indicated 4.6(46%), 2.6(26%), and 0.2(2%) mortality rate after 24, 48 and 72 hours of exposure, respectively. This showed that the mortality rate was concentration- and time - dependent as highest mortality rate of the larvae 8(80%) was recorded in 1250 ppm after 24 hours. The concentration response larvicidal bioassay of the extract at 72 hours was 0.2 (02%) mortality at 574 .0 ppm at LC50 and 4138 at LC95, compared with  control which contained only the larvae in distilled water without extract that showed no toxicity. This study demonstrated that Ocimum basilicum leaf extract possesses strong larvicidal potential and therefore supports its folkloric use as a larvicide. It is thus, a more eco-friendly alternative to synthetic pesticides, thereby contributing to sustainable malaria vector control strategies.